I just wanted to share a book I read last year. It had a great impact in the way I approach work and concentration in general. Sometimes we think that we can naturally concentrate on things if we want to, it's a just a matter that "Yeah, yeah... I have to do that more". This author advocates that concentration is a skill like any other and it needs to be exercised.
The book is Deep Work, by computer scientist Cal Newport. If you're not in the mood for a whole book, I suggest checking some of his posts in his blog (see link below).